DescriptionThis astronomical regulator has bolt-and-shutter maintaining power with a deflector arm unique to Ellicott regulators. The deflector keeps the bolt from ratcheting across the tips of the teeth of the center wheel as it is being engaged. Also unique to some Ellicott regulators (such as this one) is a special temperature compensated pendulum invented by Ellicott and made of brass and steel. The clock movement has a Graham deadbeat escapement with a large escape wheel (3-inch diameter). There is a crossed-out pulley for lifting the weight.

The silvered clock face is engraved. There are separate dials and hands for the minutes, seconds, and pendulum regulator. The hours appear on a silvered disk exposed through a curved window on the main dial.

The mahogany case has a stepped bonnet capped with three brass finials shaped as flames. There is beveled glass in the bonnet and doors.

A small envelope in the bottom of case, contains parts from the breakage of the pendulum bob in 1980 and one brass pilaster.

The winding key is not original.

(For detailed descriptions of the movement and parts, consult the captions to the photos.)

Historical AttributesThis regulator has the special pendulum invented by John Ellicott and described in the Philosophical Transactions (1753). Ellicott used a system of steel and brass rods and levers to raise or lower the pendulum bob to compensate for temperature fluctuations.

Purchased by Harvard College for £35.14.0 in 1765 with the help of Benjamin Franklin, the clock was used by John Winthrop to observe the Transit of Venus from Cambridge in 1769. The clock was also taken on several research expeditions, including that of Professor Samuel Williams to observe a total solar eclipse in October 1780 on Long Island in Penobscot Bay, Maine.